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  • Giles Henry

What is Thoracic Outlet Syndrome?

Before we start talking about this syndrome, symptoms, and treatment, we need to understand what and where the Thoracic Outlet actually is.


If you're talking to an anatomist, they will tell you about an area located at the top of the thorax called the thoracic inlet, and another area located at the bottom of the thoracic cage called the thoracic outlet. However, from a clinical perspective it is the area at the top of the thorax, near the shoulder, that is known as the thoracic outlet.


The thoracic outlet is an area of the body defined by boundaries. These boundaries are thoracic vertebrae 1 (T1) posteriorly, the first rib laterally, and the manubrium at the top of the sternum anteriorly. The area between these boundaries is known as the thoracic outlet. This is an important area as a number of neurological and vascular structures pass through here. These include branches of the brachial plexus, the subclavian artery, and the subclavian vein. Included in the the thoracic outlet area is a geometric structure known as the Inter-scalene triangle.


The scalenes are a group of 3 muscles (anterior, middle, and posterior) that attach from the transverse processes of the cervical spine to the first rib. They lie behind the Sternocleidomastoid (SCM) on the neck. The shape of the scalene triangle is defined by the anterior scalene, the middle scalene, and the first rib where they attach (see image below).



The Inter-scalene triangle

This area is important because 2 important things pass through it. The subclavian artery and the brachial plexus (specifically the lower trunk of the plexus). It is important to note that the subclavian vein does not pass through the inter-scalene triangle, but rather it passes anteriorly to the scalenes and over the top of the first rib. It is still however passing through the thoracic outlet. This can also be seen in the above image where the vein is shown in blue.


Here is a useful and brief video explaining the boundaries of the thoracic outlet and the Inter-scalne triangle.




Classifications of Thoracic Outlet


Now that we have a clear idea of where the thoracic outlet is, we can look at what constitutes thoracic outlet syndrome (or TOS). TOS can be classified into either:


1. Neurogenic thoracic outlet syndrome, or

2. Vascular thoracic outlet sundrome.


Vascular TOS is much rarer than the neurogenic type and accounts for only around 2-3% of all cases. It refers to the compression of vascular structures which lead to circulatory problems down the arm. Of these 2-3% of cases some are classified as Non-specific TOS. This refers to people who have arterial problems in their arms and possible blood clots. The most common symptoms of vascular TOS are:


1. Swelling of the arm

2. Cyanosis - a blueness of the extremity (in this case the arm).


Neurogenic TOS accounts for around 97-98% of all cases. This type of TOS refers to compression of nervous structures leading to the common following symptoms.


1. Pain

2. Full or partial parathesia (like pins and needles or a 'dead' feeling in the arm).


It is often the case that clients will experience these symptoms upon waking in the morning. This is explained a little later in the article.


Before continuing it is necessary to add another classification for thoracic outlet syndrome. TOS can be divided into Congenital TOS and Symptomatic TOS. The differentiation here is that congenital TOS is caused by structural abnormalities in the body.


1. Enlarged scalene muscles which will reduce the size of the inter-scalene triangle and thus cause compression.

2. Cervical ribs

3. Enlarged transverse processes on the cervical spine.

4. A bump instead of a groove on the first rib, which causes a reduction in the costo-clavicular space (the space between the first rib and the clavicle).


All of these four points have the same effect - to reduce space and impinge on structures making their way out of the thoracic outlet. The most common here is number 4. Often surgical intervention will be required here in order to smooth the bump and increase space in this area, but not always.


Symptomatic TOS is caused by postural dysfunction and the symptoms are more intermittent. Forward head postures, upper body cross syndrome all so prevalent in our flexion addicted society, will lead to a reduction in space in the thoracic outlet. In general the worse the posture gets the more prevalent and intense the symptoms will become. As therapists it's this classification we will spend most of our time dealing with as we have far more control over this than we do with congenital factors. It should be noted that an improved posture and treatment can be of benefit to those with congenital TOS, but many people in this category require medical treatment. Anyone presenting with TOS like symptoms, particularly if the symptoms are severe or of the vasuclar type, should be advised to see a doctor as soon as possible.



Rounded shoulders and forward head posture leads to reduced space and problems in the thoracic outlet

Nerve Trunk Compression


As mentioned earlier some people who experience symptoms of neurogenic TOS often feel those symptoms in the morning when they wake up. This is the difference between what we call nerve root compression and nerve trunk compression. When the root of a nerve is compressed the person will feel a quick shooting like sensation/pain down the arm. However with nerve trunk compression, the feeling is more cramp like, pins and needles, or a 'dead' arm. Nerve root compression symptoms are felt when the nerve is compressed. However nerve trunk compression is felt when the pressure is released from the nerve. This is why it's felt in the morning or sometimes during the night when you are sleeping. Let's look at an example.


Dave has poor posture and spends much of the day hunched forward at his desk. His forward head posture and rounded shoulders cause the space in the thoracic outlet to reduce and cause compression on the nerve trunk. However this will typically be asymptomatic at the time. When Dave goes to bed and lies down, the pressure is gradually released from the trunk and during the night or when he wakes up, Dave will experience the symptoms of neurogenic TOS. When he stands back up again the compression on the trunk reoccurs, and the symptoms actually dissapate.


Can I do anything to alleviate the symptoms myself?


It follows of course that if symptomatic TOS is caused by bad posture, then improving one's posture is the way to go in terms of correcting it. There are four main things you can do to help yourself improve your posture in this region, and hopefully remove the symptoms of TOS.


1. Stretch the chest and shoulder areas to try and create some space. A good way to do this is to kneel down and place the hands on the floor behind you. Have the fingers pointing away from your body if possible. The further away from the body the hands are the harder this stretch will feel, so be sure to start with something that is ok for you to hold without too much strain. When in this position you should try and pull the shoulder blades together to help open the chest. Hold this position for 30-40 seconds maintaining breathing throughout. If you cannot kneel down for some reason, try to have the hands behind you in a standing position and turn the hands palm up. Pull the shoulder blades together here for a similar stretch. You should also do the stretch from standing if this position exacerbates any symptoms you feel in the arms.



Kneeling chest stretch


Standing chest opener

2. Stretch the scalene muscles of the neck. The best way to do this is from a seated position. Sit on a chair, bench, or the end of the therapy table. Hold the side of the chair and side bend the head to the opposite side to the arm that's holding the chair. This will stretch all of the scalenes particularly the middle one. Rotating the head away from the holding arm slightly while side bending will target the anterior scalene more, while rotating toward the arm will target posterior scalene. However the simple side bending move will do a pretty good job for all three.




Seated scalene stretch with slight rotation

3. Train your back muscles. In people with rounded postures their chest muscles are typically stronger than the inhibited and weak back muscles. This is particularly true of people who go to the gym and spend far too much time on working their chest, biceps, and anterior shoulders. Home exercises without equipment can be used, as can bands, weights, or more advanced equipment like suspension trainers. Below are a few examples of exercises that could be beneficial. Remember, it's always better to get advice from a qualified professional especially if you're exercising for the first time.


1. The cobra stretch



Cobra stretch

2. The back raise



For beginners keep feet on the floor

Suspension trainer pull exercise (narrow grip)

The Lat Pulldown

There are many other exercise that could be included. Always seek professional help when starting on a new exercise program.


Lastly, minimise activities that cause poor posture. This is the hardest one. Posture is habit built up over time. In reality, even if you are doing exercises that counter some of the effects of bad posture, continually engaging in things that promote it will be like trying to ice skate uphill. Correcting your posture requires more awareness in your day to day activities. Here are some things that you can focus on.


Prolonged sitting. If you sit at a desk all day, especially if you are writing or working on a PC, then you can help yourself by doing 2-3 basic things. Firstly, get up and stand every so often. You don't have to stand up for long, just 30 seconds will do. When you stand up you break out of that typically flexed forward posture and have a chance to stretch up and open the chest. It will also give your hip flexors a chance to lengthen. The longer you stay seated without a break the worse the shortening of some anterior muscles will become.

Secondly, be aware of posture while you are seated. Try to keep the chest up and reduce hunching over.

Thirdly, make sure the desk, seat, and monitor height are suitable for you. If they are too low for example, it will become very difficult not to hunch over in order to do your work.


Standing posture. Try to become more aware of what's going on with your posture when you stand or walk. This is hard to do at first but you'll notice the difference when you stand a little taller or lift the chest. Now I'm not advocating that you stand like a Sergeant Major or ballet dancer, but that awareness of just holding the chest a little higher can make a big difference. Keeping that position might start to make you aware of some muscles you didn't know you had!


Breathing. Better breathing = better posture and vice versa. We already have too many mouth breathers in the World and you don't need to be adding to their numbers!


Now using the mouth to breathe is sometimes going to be needed, for example during more intense bouts of exercise. Typically however you should be using the nose to breathe, especially on inhalation. Breathing in through the nose and out thorugh the mouth is also ok. Try walking around and breathe through the nose. As I tell my clients, unless you're eating or talking your mouth should be mostly shut.

Diaphragmatic breathing is the way to go here. This type of breathing refers to breathing where the diaphragm is activated. Nasal breathing activates the diaphragm in the most effective way (sheet like muscle separating thorax from abdominal cavity) which is very important. This muscle forms the 'lid' of the core and will 'switch off' if not used. You end up as a chest breather which is far less efficient. Nasal breathing accesses the deeper capillaries of the lungs, and there is no filtration of breath if it goes through your mouth. So to keep the diaphragm active, stay healthier, and maintain better posture, nasal breathing is better, with nasal inhalation and mouth exhalation a decent second. It can also help to reduce stress.

Specific breathing exercises can help with training this. For a more detailed explanation, you can check out this vid from Underground Gym



Getting Professional Help


Sports massage and myoskeletal alignment therapy can be of great benefit to not only correct postural imbalances, but in turn relieve the problems associated with symptomatic TOS. There will be times when fascial adhesion, shoulder immobility, and inhibition in opposing muscles will need to be treated by a professional for the best and most lasting results. A quality therapist will also be able to advise you on the type and frequency of exercise and homecare you need to engage in.

I have personally achieved excellent results when helping a number of clients with this condition. As always prevention is better than cure so a good therapist will identify possible postural problems and seek to correct them before nasty conditions like TOS can have any real impact.

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